I am assuming the conductors are #10 or larger(depending on the distance from the contactor), so 40A would be proper protection. 15A O/L on a 12.7 FLRA is around 125%, which should be correct as well. Blowing fuses on startup would indicate that there is a short somewhere(fuses can take a limited amount i of inrush). You could try engaging the contactor with the leads disconnected at the motor. This will let you know if the cable is good up to that point. It is a good idea to meggar the cable before it is re-energized. Also check the contactor for any carbon tracking and that it will move in and out freely. Check the resistance of the motor windings, making sure they are balanced. There is also the posibility that the control transformer is shorted (480-120VAC most likely). Try to eliminate each component until you find the culprit.
I hope this helps and good luck...if it is really important, I'm not afraid of flying

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Everyone has their own rhythm....so find it and lets jam

Well, of course it's do or die. We have been trying to get them to buy us a spare pump for a while. But they have to make our lives a PITA. Boss wants to get a good megger now though.

Tried it with the motor disconnected and no problems with the fuses. It isn't VFD controlled. Learned recently that they can generate voltage and destroy bearings, so our 125 hp motor has a grounding brush on the shaft. I tested the windings at .8 ohms across all 3 phases. Boss got around 1.2 ohms. Could be the contactor. Lead wires are 10 gauge I'm pretty sure of.

Just had to replace a 100A circuit breaker because it was tripping. Internally it got fried. This was for another piece of equipment.

Electrical gremlins have been kicking my ass lately.

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Quote:

Originally posted by burgerking So?
Holland is about the most expensive country in Europe when it comes to bikes and fuel..Stop whining and go riding It's just money and you only live once...